Potassium-bichromate process of photographic reproduction



. rectly from a negative.

lhttiidill f S @ATNT @FFHQE ROBERT JOHN, OF NEW YORK, N. Y., ASSIGNOR T0 DAYLIGHT FILM CORJPGRATION, A

CORPORATION OF NEW YORK.

POTASSIUM- BICHROMATE PROCESS OF PHO'IOGRAPHIC ItElePROIDUC5310 Ito Drawing.

To all whom it may concern:

Be it known that 1, ROBERT J OHN, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a certain new and useful Potassium-Bichromate Process of Photographic Reproduction, of which the following is a specification.

My invention relates to a potassium bi ohromate process of photographic reproduction and has for its object to produce a printing surface containing a photographic record of lights and shades from which copies can be made by a dye or ink contact transfer process. An illustrative dye contact transfer process is disclosed in patent to Shepherd and Bartlett, No. 728,310, granted May 1.9, 1903, for photographic printing, and an illustrative ink contact transfer process is disclosed in Cassells Cyclopaedia of Photography, Cassell & Co. New York, 1912, at page 124 wider the title Collotype, it being understood, however, that the processes thus illustrated do not use a printing plate having the novel and beneficial characteristics of the printing plate disclosed herein. Although the preferred method is to obtain the photographic I'ecord for the printing surface from a completed negative, it may be obtained by direct exposure, as, for example,in a camera, the details of which method are disclosed in a copending application for Letters Patent Serial No. 327,890, filed October 2, 1919, for process of photographic reproduction di- The printing surface when treated with dye or ink also may be used in the same manner as a positive, either for direct view, or with reflected light, or with transmitted light as in a projecting machine.

The invention is applicable to monochromatic, polychromatic, or natural color photography both in still photography and in motion picture photography. The term color is intended to include black, which sometimes technically is designated as an absence of color.

In the embodiment of my invention chosen for purposes of illustration, a sensitized emulsion such as a silver salt emulsion is exposed to the action of light modified by the lights and shades of the completed negative which it is desired to reproduce. The silver salt emulsion may be carried or -lose base, in order that Application filed October 2, 1919. Serial No. 327,889.

mounted on any desired support, either opaque, translucent, or transparent, but preferably is mounted on a transparent carrier such, for example, as glass or a celluthe silver salt emulsion may be exposed to the modified light through its transparent carrier.

The emulsion then is developed in well known manner by any non-hardening develope-r until desirable metallic silver image is obtained and preferably is suitably fixed to remove the unreduced silver.

The emulsion then is treated by a solution containing an agent which renders insoluble or unremovable the emulsion adjacent its metallic silver content, the effect of which agent is controlled or limited selectively by the presence of varying quantities of a neutralizing agent, after which the soluble or removable portions of emulsion are removed in any desired manner, as, for example, by melting with warm water.

The result of the above treatment is the production of what may be termed a printing surface having novel characteristics and beneficial properties never before attained.

The most important of the novel characteristics is a printing surface comprising granules or great numbers of photographically formed, extremely minute, individual protuberances which are distributed and grouped irregularly so as to represent photographic lights and shades.

The most important of the beneficial properties is that such a printing surface when treated with a dye, ink, or other coloring matter, will absorb or take up or carry the coloring matter within a few seconds, and when thus treated and placed in contact with a substance which is to carry the final reproduction, such for example as gelatin, will give up its coloring matter practically instantaneously and produce on said gelatin an exact and perfect reproduction. This speedy result, which is novel and was impossible of attainment before the present invention, is of prime importance in the production of motion picture positives from motion picture negatives, although the saving of time and the superior results obtainable in still photography also are important. The printing plate or film, moreover, when treated with coloring matter, may be used as a positive if reproductions are not desired.

till) Nil A sample formula for a treating solution containing a hardening or tannmg agent the effect of which is controlled and limited selectively by the presence of varying quantities of a neutralizing agent is as follows:

Water 20 ounces- Potassium bichromate 1024 grains Sulphuric acid- 3 to 4 ounces Water 1 to 32 ounces Add four (4:) ounces of above solution to twenty-eight (28) ounces of water. Use half and half with water. In the above sample formula the hardening or tanning agent is potassium bichromate, and the controlling and limiting agent is sulphuric acid which may be varied in amount selectively within limits to obtain the desired result. Other hardening and tanning agents and other neutralizing agents may be used, the above formula representing one treating solution by which the process may be carried out. Hydrochloric acid, for example, as well as other acids may be used, the above formula representing one treating solution by which the process may be carried out. The tanning or hardening effect of potassium bichromate on the emulsion surrounding a metallic silver was known previous to my invention, but the method of controlling the tanning or hardening effect so that a too contrasting or paddy relief was obviated and the desired granular printing surface obtained was not known previous to my invention. Thus if potassium bichromate without any sulphuric acid or with only a very little sulphuric acid is used to treat 'metallic silver in an emulsion, the tanning or hardening action is so great that a too contrasting or paddy relief is obtained. As more acid is added, however, the relief becomes thinner until the point is reached where the amount of acid added produces a relief characterized by the granular printing surface desired. If acid is added beyond this point, the tanning or hardening effect of the potassium bichromate will be neutralized entirely so that all the emulsion would dissolve from the carrier when treated with warm water.

It is believed that the hardening or tanning effect of the potassium bichromate exerts its action first adjacent the particles of metallic silver. The potassium bichromate 7 probably reactswith the metallic silver to as above set forth, only the particles of emulsion adjacent the said metallic silver are hardened. The unhardened portions, as stated above, then may be removed in any desired manner as b .placing the emulsion in warm Water which causes the unhardened or soluble portions to soften and melt away from the hardened or insoluble portions so that the hardened emulsion alone will remain in the form of extremely minute, individual protuberances which are distributed and grouped irregularly so as to represent the photographic lights and shades which it is desired to reproduce. It is preferable that only those portions of emulsion be hardened which are adjacent the carrier for the emulsion, which may be accomplished in various ways, some of which are disclosed in my copending applications for Letters Patent Serial No. 313,239, filed July 25, 1919, for a thin mounted sensitized emulsion; Serial No. 313,240, filed July 25, 1919, for process of making a contact transfer printing surface by complementary light; Serial No. 327,891, filed October 2, 1919, for potassium iodide formula for photographic processes, process of using same, and article obtained thereby; Serial No. 332,806, filed October 23, 1919, for process of making a contact transfer printing surface with a colored emulsion, and among which may be mentioned the exposure of the sensitized emulsion through its transparent carrier and the limitation of the depth to which the rays of the exposure light penetrate by having the actinic rays of exposure light and the emulsion complementary in color.

Although the treating solution referred to acts also as a bleach, the hardened emulsion may be bleached further if desired to remove any black metallic silver not already bleached. This may be done in well known manner, and while not necessary, is of advantage as it enables the operator to watch the effect of the coloring matter on the printing surface to which it is applied for carrying out the printin rocess. The order of melting, leaching, and fixing is not important and may be carried out in any order desired, although it generally is more convenient to fix, bleach, and melt, in the order named.

- The printing of positives from the printing surface may be done by direct contact. The printing surface is exposed to the action of the desired coloring matter as by placin it in or carrying it through a liquid color ath. The colored surface then is placed in contact, preferably under some pressure, with the substance on which the positive is to be made, as by a roller or by a squeegee action. As stated above, the printing surface prepared by my process receives and gives up the coloring matter al' lit iih

Ell

incense most instantly as distinguished trons other processes which take an appreciable length of time.

Natural color edects may he produced in well known manner, such for example as by exposure through color screens with sub sequent treatment and manipulation to oh tain the desired results.

Many modifications of my invention will he apparent to those skilled in the art without departing therefrom or from the scope of the claims, my invention not being limited to the embodiments thereof chosen for purposes of illustration but consistin ot a process for forming a printing sur ace capable of acquiring and giving up a desired color with great rapidity by treating an emulsion with a selectively controlled agent which hardens the emulsion adjacent metallic silver particles therein.

Having described one elnhodiment of my invention, what I claim is:

1. The process of forming a photographic record of lights and shades capable of use as a transfer printing plate, which oomprises developing an exposed photographic emulsion with a non-emulsion hardening solution and then treating portions of emulsion adjacent the light afi'ected sensitive con tent of the emulsion with an agent adapted to harden said emulsion by reaction with the light ailected sensitive content of the emulsion, and with a neutralizing agent for said hardening agent, the relative proportions of said agents losing such as to control selectively the effective area 0t influence ot the harden ing agent but to an extent less than the complete neutralization oi said hardening agent.

it. The process specified in claim it which the sensitive con ent is a silver salt.

3. The process specified in claim it which the hardening agent is potassium hichromate,

d. The process specified in claim it a which the neutralizing agent is an acid.

5. The process specified in claim )1 in which the neutralizing" agent is sulphuric acid.

6. The process specified in claim 1 in which the hardening agent is potassium hichromate and the neutralizing agent sulphuric acid,

7. The process specified in claim l in which is added the step of removing theunhardened portions of emulsion suhsequent to said treatment.

In testimony that )1 cl the foregoing l have hereunto set my hand this 30' day of September 1919.

RGBERT JQHN.

hardening and neutralizing 

